ExxonMobil has agreed to pay Fort Worth’s famed Bass family as much as $6.6 billion for 275,000 acres of oil and gas leases in the Permian Basin.

The deal announced Tuesday more than doubles the Irving-based giant’s Permian Basin reserves to about 6 billion barrels. The Bass lands are estimated to have 3.4 billion barrels. The property is located mostly in New Mexico’s Delaware Basin.

In a written statement, ExxonMobil Chairman Darren W. Wood described that area as a “dominant U.S. growth area for onshore oil production.”

Baker Hughes' real-time rig map shows the high concentration of drilling activity in the Permian Basin in West Texas.

Officials with Bass Enterprises Production Co. declined to comment on the sale.

The purchase gives ExxonMobil a better economy of scale in that field to help account for low oil prices. It's ExxonMobil biggest deal in six and a half years.

"By utilizing ExxonMobil's technological strength coupled with its unconventional development capabilities we can drill the longest lateral wells in the Permian Basin, reducing development costs and increasing reserve capture," according to a statement attributed to Wood.

The Permian Basin has attracted nearly 25 percent of worldwide oilfield acquisition spending in 2016, according to Wood Mackenzie Ltd. New technology has increased oil drilling in shale formations just as it did earlier with the Barnett Shale and other sources of natural gas.

There was also some financial optimism in the petroleum industry this week. Oil prices increased Tuesday after officials in Saudi Arabia announced that an OPEC agreement had been effective in cutting production. There were also expectations for increased demand, according to the Saudi energy minister.

Some non-OPEC countries also committed last month to reducing production as a way to increase prices.

The Federal Reserve Bank of Dallas also described a "dramatically" improved outlook in its fourth quarter energy survey released Dec. 29. The data was collected from 147 energy companies.

After declining all year, oil and gas production started increasing in the fourth quarter. Some respondents did questions the prices paid for leases in the Permian Basin though.

"The Permian transactions are approaching price multiples associated with a bubble or a Ponzi scheme," one energy company representative wrote.

Others express lesser or no concerns about the prices.

In August, Concho Resources paid $1.625 billion in cash and stock for rights to drill on 40,000 acres in the Permian Basin. That same month, Parsley Energy spent $400 million for rights to 11,672 acres in that region.

It's not clear how this sale fits into the Bass energy strategy since officials did not comment.

The Basses are one of Fort Worth's most prominent families. They gained national reputations for their business skills - inside and outside of the oil and gas industry - as well as for their philanthropy.

Downtown Fort Worth's Bass Performance Hall was named for the family. And in 1991, to celebrate their 50th wedding anniversary, Perry and Nancy Lee Bass donated $1 million each to 50 different charities or civic institutions.

This Exxon deal gives the Bass family's company $5.6 billion in ExxonMobil shares and contingent payments of up to $1 billion. That cash portion would be paid starting in 2020 and ending no later than 2032. Those payments would be based on production on those former Bass leases.